How did you come to that conclusion? In Swift 2.1 (I'm late to update), with
optimizations on, this function:
> func test() -> Double {
> return Double(arc4random())
> }
compiles to this IR:
> define hidden double @_TF4test4testFT_Sd() #0 {
> entry:
> %0 = tail call i32 @arc4random()
> %1 = uitofp i32 %0 to double
> ret double %1
> }
which has no allocation at all.
Félix
> Le 28 mars 2016 à 07:05:48, Biala via swift-evolution
> <[email protected]> a écrit :
>
> After few days playing with the profiler I have noticed some shocking swift
> behaviour.
> When casting basic types from one type to another, for example from Int to
> Double swift is actually creating and then deallocating something :( That
> leads to another performance problem - imagine many casts in loops.
>
> As a type strict language swift is forcing one to cast Int to Double to when
> you multiply double by Int variables for example but as the cast is so
> expensive what should developers do to get better performance for some bit of
> code. As a sound processing developer I see most of the real time sound
> processing moved to C++ code, but I don,t see the reason for that as it is
> most basic operations in loops. Swift needs to be faster to become serious
> language ...
>
> After profiling here is what I see:
>
> 1. slow arrays - may be partly improved using UnsafeMuttablePointers
>
> 2. expensive cast - this is not possible to avoid at this point. I will
> suggest making the language not so type strict when there is no need (like
> adding int to double and so on)
>
>
>
> array[i] = value
> Double(1)
>
> These problems come from hidden function calls so please avoid adding more of
> them in future like the syntax Erica suggested for the if:
>
> if v in (0...127)
>
> I suppose that the range will be also created and then deallocated in
> background.
>
>
>
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